Various polymers, swellable clays, and articles of manufacture have been applied to the surface of soil to provide a waterproofing layer to prevent substantial penetration of water and hazardous or toxic materials into the earth in order to provide lagoons, ponds and hazardous or toxic waste containment areas. Water-swellable clays, such as bentonite, have been applied directly to the soil surface and impacted in place, as disclosed in this assignee's prior U.S. Pat. No. 3,986,365. In addition, many different multi-layered articles of manufacture containing a water-swellable clay, such as bentonite, have been manufactured by adhesively securing the water-swellable clay to a flexible sheet material for application to the soil surface in abutting or overlapping relation to adjoining multi-layered articles. Examples of flexible sheet materials containing adhesively secured water-swellable clays are found in the following U.S. Patents: Clem U.S. Pat. No. 4,467,015; Clem U.S. Pat. No. 4,501,788; McGroarty et al. U.S. Pat. No. 4,693,923; Harriett U.S. Pat. No. 4,656,062; and Harriett U.S. Pat. No. 4,787,780.
Another waterproofing barrier disclosed in Blais U.S. Pat. No. 4,344,722 is constructed in the field by applying a first flexible, water-permeable fabric layer, overlaying a thickness of powdered or granular water-swellable clay material and applying an upper or overlayer of the same flexible, water-permeable fabric thereover. Other patents disclosing the use of substantially water-impermeable layers for protecting a soil surface include British Patent Specification 1,059,363; British Patent Specification 1,029,513 and British Patent Specification 1,129,840.
As set forth in this assignee's U.S. Pat. No 4,094,382, water-soluble industrial wastes, particularly at relatively high concentrations, can substantially increase the water-permeability of water-swellable clays, such as bentonite. Thus, when the water barrier characteristics of a water-swellable clay is most important--that is, when used to contain a substantially contaminated pond, lagoon or hazardous or toxic waste containment area, often times the clay allows seepage of a substantial amount of the contaminated solution into the soil, sometimes resulting in the contamination of valuable ground water supplies.
Attempts have been made to prevent the seepage of contaminated water through the water-swellable clay so that the contaminants would not find their way into ground water supplies. An example of an attempt to improve the water barrier characteristics of water-swellable clays when subjected to a head of water contaminated with water-soluble inorganic industrial contaminants include this assignee's U.S. Pat. No. 4,084,382. An article or process for preventing contamination of ground water supplies has been in need for many decades and is becoming more and more critical as time passes due to the even smaller supply of potable water in many areas of the United States, and throughout the world.
While others have attempted to prevent the seepage of contaminated water through the water-swellable clay material or layer as a means of protecting the ground water supply, quite surprisingly, applicant has found that the ground water is protected from contamination in a very unique and unobvious manner by an in situ in-ground treatment step, by treating the contaminated water that enters or passes through the water-holding material, e.g., a water-swellable clay layer with one or more materials capable of absorbing, adsorbing, ion-exchanging, neutralizing or reacting with the water-soluble contaminant(s). To achieve the full advantage of the present invention, the contaminant treating material should be dispersed above the soil or containment area floor as a separate layer and not admixed with the soil in order to make sure that the contaminants will be treated and not find a circuitous path through the contaminant-treating material to the ground water without being completely decontaminated.